As it is known by those skilled on the art, most part of the hermetic compressors, usually applied on cooling systems, comprises at least one acoustic attenuating device disposed inside the carcass, particularly on the suction line and/or exhaust line, being the main purpose of this device attenuate pumping pulses of coolant gas to reduce the hermetic compressor noise, and also thermally isolate the coolant fluid.
Just for clarification, this type of acoustic attenuating device can present different nomenclatures, specially, depending on its installation position related to the compression unit. For example, the terminology suction acoustic filter or suction muffler are usual when the referred attenuating device is positioned on the suction line, in a way to promote the coolant gas conduction from strainer on the direction of the suction valve. When said attenuating device is positioned after the compression unit, nomenclatures are adopted as expansion chamber or expansion muffler, or also can be named as exhaust chamber or exhaust muffler.
On this context, is it seen that the acoustic attenuators device applied in compressor well known on the prior art comprises constructive and functional configurations really complexes that affect, mainly, the production lines and compressors assembly and, consequently, of equipment and cooling systems in general. More particularly, appears that the devices from the prior art comprises structures of reduced dimensions which ends up requiring precision levels and components finishing substantially high to obtain the security in conducting and directing coolant gases, besides the acoustic attenuation and, eventually, on thermal isolation of these gases.
More specifically, it is known that these acoustic attenuating devices are formed by a hollow body in which are provided chambers and ducts for coolant gases circulation from, and to the compression unit. As it is broadly known by those skilled on the art, this gases circulation is caused by compression chamber pulse, which generates noise that are softened as the structural and geometrical features of ducts and chambers through which gases circulate, this is, the attenuation level of noises can be higher or lower according to the specificities and the constructive details of the acoustic attenuating device applied on the compressor.
On this context, as above highlighted, it can be said that this inconvenient are particularly related to structural aspects for manufacturing and assembling this chambers and coolant gases circulating ducts. This is because, this chambers and ducts are formed by several pieces and walls that should be fitted together in a way to obtain an adequate geometry of chambers and ducts for the correct acoustic attenuation inside the attenuating device.
However, in view of the quantity of inter-related pieces, there is an excessive number of interactions needed between pieces that ends up favoring internal leaks of gases, in other words, as should be known by those skilled on the art, as higher the number of interactions and connections between pieces, higher the risk of providing vulnerable regions and capable of causing leaks, affecting directly the levels of acoustic attenuation, but mainly the work conditions of the compressor.
For example, there are known on the prior art the documents US 2005/0031461, U.S. Pat. Nos. 5,201,640, 5,971,720 and 6,506,028, that reveal models of acoustic attenuating devices developed for applying in hermetic compressors. Despite being functional, this models of device presents inconvenient related to the sealing level between the internal chambers and formed ducts, once this sealing are obtained just by material interference contact, what needs really precise geometry and, consequently, affecting the production line.
Another inconvenient of these devices from the prior art is related to the configuration and shaping of internal ducts for gas circulation, which ends up needing applying some intermediate further pieces to form an acoustic filter for attenuating properly the pulses coming from the compression system, causing determined excitation to the compressor set that, in the end, when functioning, will have a determined acoustic behavior (perceptible to human being) that in real is a noise spectrum because of frequency. As a result, it is needed an increase on the number of sealing between components, affecting directly projects and manufacturing and assembly costs of these devices.
In order to solve the most part of the inconvenient above related, it was developed an acoustic attenuating device, which is also the object of patent document BR102013019311-9 filed by the Applicant itself. More particularly, this attenuating device managed satisfactorily solve the inconvenient observed on production lines, as well as the attenuation levels of pulses coming from the gas compression system.
The device developed and defined by the patent document from the applicant itself achieved these objectives because of the concentric pipes disposal applied for connection between the acoustic chambers and the hollow body that forms the attenuating device. More specifically, said acoustic chambers are formed by the disposal of an intermediate element, which is formed by a platform having at least one connection channel that is fluidly connected between the acoustic chambers and surrounds the output channel that is connected to the output port.
As should be appreciated by those skilled on the art, and as explored on document BR102013019311-9, this concentrically relation between the connection channel and the gas output channel, in order to obtain the proper geometry of the chambers, ducts and volume inside the muffler to correct acoustic attenuation.
Despite showing very functional referring to noise attenuation and, mainly, simplifying the manufacturing and assembly lines of acoustic attenuating devices, in practice, it was seen the possibility of further improve this type of device, particularly in reference of the control of said “external circulation of oil”—CEO and, also, improve acoustic attenuation levels.
As should be known by those skilled on the art, this CEO is the percentage of pumping oil together with the coolant fluid inside the cooling system, once that, inside of the compressor has bearing lubricating oil. In case this percentage of CEO exceed a predetermined value, the level of oil inside the compressor can decrease and, with this, endangers the integrity of functional components of compressor, in view of the low index of lubricating.
An alternative that was seen to compensate the increase of CEO percentage would be increase the quantity of oil inside the compressor. However, this solution does not seem profitable in view of the increase on the compressor final costs, in addition to let it next to the electrical engine that may cause noise increase. Another problem in increasing the amount of oil on the compressor is provide the inflow of oil on the suction chamber, that would cause blow liquid and compressor break.
Particularly related to the attenuating device model, according to object of patent BR102013019311-9, in some moments during the functioning, this percentage reached higher levels due to concentric disposal of connection channels and output, once such disposal generated a region between surfaces that facilitated conduction of oil to the cooling system.
This concentric condition favors oil pumping, once the fluid flow strength by contemplated region between the intermediate pipe and by the pipe connected directly on the headstock, which in turn has the lower pressure values inside the chamber. Other constructions has also advantage related to oil purge from inside the chamber comparing to this construction due to the distance between the pathways that the fluid (coolant gas with oil) runs until finding the pipe connected directly to headstock.
This way, considering the above related, it is possible say that the acoustic attenuating devices for hermetic compressors, according to available knowledge of the prior art, presents limitation and constrains that affect directly the manufacturing and assembly of this type of device. Besides that, other models that solve these inconvenient apparently can be improved referring to functionality, and specially related to problems from the CEO percentage control.